Device for finely setting compass points



March 22, 1949. A. s. MCDONNELL DEVICE FOR FINELY SETTING COMPASS POINTS /I////////////////If Patented Mar. 22, 1949 UNlTED STATES ears EFHCE DEVICE FOR FINELY SETTING COMPASS POINTS Aloysius S. McDonnell, Chicago, Ill- 9 Claims.

This is a division of my copending application Serial No. 483,728, filed April 20, 1943, now Patent Number 2,370,741, issued March 6, 1945.

The present invention relates to a device for setting compass points to a very fine degree of accuracy.

Among the objects of the invention is to provide a novel device having graduations or graduation lines which may be arranged in a circular or annular series with a coordinated setting line having a given variant relation to a base or datum line whereby the points of a compass, such as a beam compass, or a divider, or a trammel, and the like, may be set to a minute degree of accuracy.

Other objects, advantages, capabilities, and the like are comprehended by the invention as will later appear, and as are inherently possessed by the invention.

Referring briefly to the drawings,

Fig. 1 is a top plan view of a device constructed in accordance with the invention;

Fig, 2 is a view in section taken in a plane represented by line 2-2 in Fig. 1 of the drawings;

Fig. 3 is a fragmentary plan view on an enlarged scale of the essential parts of the embodiment shown in Figs. 1 and 2;

Fig. 4 is a top plan view of an alternative embodiment of the invention; and

Fig. 5 is a sectional view taken in a plane represented by line 55 in Fig. 4 of the drawings.

It is customary for a mechanic or an engineer to set the points of a beam-compass, a dividers, a trammel, and the like, by using a graduated scale; but such a scale as the mechanics and the engineers generally use, comprises among its graduations one set containing 100 graduation lines per inch, but is not graduated finer than such 100 lines per inch. Thereby, it is difiicult to set the compass points accurately to any greater degree of fineness than /100 of an inch. It is also impractical to calibrate such usual scale much finer than stated above, or as fine as several 100 lines to the inch, since then the graduation lines become too fine to construct and also become too difficult to read readily on the barshaped scale of practical size, usually 12 inches in length.

I have therefore provided my improved device whereby the points of a beam-compass and the like can be set to a much finer degree of accuracy than has been done so far with the customary means. With my invention, in either of its forms disclosed herein, I provide a special and finely graduated member and arrange it so that it can be used in conjunction with a known scale bearil'lg standard graduations, including graduations containing 16 lines to lines per inch; and either of such graduaticns on such scale may be conveniently used with my device, whereby the compass points can be set readily and accurately to /10000 part of an inch, more minutely and accurately than was done heretofore.

Referring more in detail to the drawings, the embodiments chosen to illustrate the invention are shown as comprising a circular or annular member 4! (see Figs. 2 and 3) or 61 (see Fig. 4) respectively carrying or bearing graduations 46 and t6, and an associated scale 42 and 62, respectively, carrying or bearing graduations 43 and 63, as shown.

The scale 42 and 62 may be of the customary and standard bar shaped or straight edge construction and bearing the usual graduations 43 and 63, respectively, and these graduations may be 100 to the inch.

More particularly the embodiment shown in Figs, 1, 2 and 3, the disc-shape member 4| is shown as having or bearin on its face 45, graduation lines 45, which extend radially and are arranged in a circular or annular series between the central portion of the disc-shaped member and its periphery, said periphery lying at the peripheral side 41 of the member 4| and serving as a datum or base line for making measurements as herein described. This annular series of graduation lines is located with its outer boundary near or adjacent the periphery or datum or base line of the member 4!, and is divided into 10 sections or segments with each section or segment preferably including 100 lines, as shown in Fig. 3, while each line 46 extends radially toward the side'or datum or base line 41 against which the end of the scale 42, which is the zero graduation thereof, is abutted whereby said end constitutes a datum or base line which is tangent to said datum or base line H at a point where a scale line 46 extended intersects at right angles to said end or side or datum or base line at said end of the scale 42. Where the companion scale used has its graduation lines comprising 100 to the inch, then these graduation lines 46 need not extend entirely around the face 45, as shown in Fig. 1, but only over a section or segment thereof which comprises 100 graduation lines 46 and covers 36 degrees of the 360 degrees of the face 45 illustrated, whereby to provide for the thousandth and the ten-thousandth parts of an inch, such scale 42 provides for setting accurately to the hundredth part of the inch. 1

A setting line 48 is provided on said face 45, being near or adjacent the peripheral side or line 4'! of the member 4|, and this line is curved from one of its ends 49 to the other end 50 at a uniform rate of increase away from said side or line 41. Said setting line 48 is cut or etched in the face 45 in the form of a slight .groove, as best shown at 48 in Fig. 2, and its initial end 49 is preferably started a slight distance inward from the side 41, being indicated as a width or ofiset 5| of of an inch. The uniform inward curvature of this setting line 48 is preferably arranged so that in 360 degrees entirely around the face, the increment or space between the end parts of this line, taken radially outward of :a line 46, is 6 of an inch, and .as is indicated by the space or distance 5| in Fig. 3. Similarly, .the inward curvature progress of said setting line 48 amounts to 1/ 100 part of an inch for its length extending over e of the circular face or over 36 degrees of its face. This .device is thus also arranged for use in setting the compass points accmzately to ithe 'l/10,0'00 part of an inch.

A frame52 is provided-for rotative'ly supporting and retaining the member 4] and the-scale .42 :together in their operative position, and it includes azseat .or track or .race :53 for .rotatably'supporting said member 41 therein, and a seat or track or race '54 for [receiving therein the .scale 42 which maybe clamped in place by a clamping element 55 with amut 56. A retaining plate 51 s secured underneath member 4| and enga es beneath this frame 52 for retaining said member rotatably in its seat; while a knob 58 'is preferably provided on member-4i to facilitateturning it :to the proper position in the frame.

A "setting finger '59 may be provided and -mounted on the frame 52, and having a guide edge :60 projecting slightly inwardly beyond the inner end portion of the :seat or track or race 54 and the zero line of the scale 42,'thus providin a setting edge or 'the like 160 for facilitating the setting of the compass points.

The embodiment .shown'in Figs. 4 and .5 has a circular or-drum shaped-member 61 having an an- .nular face 65 having peripheral sides '61 serving as a datum line or base for making measurements as herein described, and the scale '62, which may be used in conjunction with this member, bears the graduation lines '63, as shown. These lines may be provided along va side of the scale only for setting one of the compass points; and the 'scale'is marked'forinc'heswith the linesarranged on 'the decimal system. The annular surface '65 hears graduation "lines '66 and the'circular edges .or peripheral limits '6! provide boundaries or sides 'or'datum lines or'bases for the face 155. The graduation lines 66 :are placed near or adjacent a side :or line 61 and extend perpendicularly t-heretaas shown.

' A setting line '68 is provided on the "face -65, being also preferably placed 'near or adjacent to the operative side or line 651, .and may 'he cut across the graduation lines, and it is curved or slanted from its initial end '60 to its final end Ml, at a uniform rate of increase away from the side or line 61. "This line .68 preferably also has :its initial end '69 placed 1 010311 inch away from the side or line 151, as shown by the ofiset 'M, and also has the final end spaced 1 6 of an :inch from the initial end '69, while the lines .56 are also suitably arranged and divided, similarly .to t'he embodiment shown iniFligs. '1, 2 and B.

A frame 7 2 maybe provided for rotatably supporting the member 61, and it includes .a seat or :and constructed for setting compass points accurately to the 1/10,000 part of an inch.

By way of illustration and assuming that it is desired to set the points of the compass apart 1.203 inches, one of the points will be set on the 1.1 inch scale mark of the scale 43 or 53, and the other point on the setting line 48 or 68 at the thirtieth division from zero of the scale graduationsAS 01- 66. This provides the setting of 1.203 inches, which includes the 1.1 inch on the scale 43 or 63,-and the 1% of an inch for the offset at the initial end 59 or 69 of the line 48 or 58, and the additional distance or increment of 0.0030 or .0.-0.03 of an inch provided by the slanting of the line 48 orfi8 at the point of the 30th division along the length or range of the scale 46 or 66.

While I have herein described and upon the drawing shown a few illustrative embodiments of the invention, it is to be understood that the invention is not limited thereto but comprehends other constructions, details, arrangements or parts, and the like without departing from the spirit of the invention.

Having thus disclosed the invention, I claim:

:1. A device as disclosed for the setting of a measuring instrument of the kind likened to a compass, comprising a support, an elongated scale member bearing a set of graduation lines with an end of said member constituting the zero graduation line of the scale graduations on said scale member, a rotatably mounted member on said support and havin a periphery which serves arbase line which is tangent with said zero graduation line of said scale member, said rotatably mounted member also having on its surface an annular series of graduation lines xtending at normal to saidbase line, said surface also having a setting line which extends at a small angle to said base line and transversely of said lines of said annular series of graduation lines on said surface at a uniform rate of increase away from said base dine, and means on said support having an edgeconstituting a guiding line which is disposed to be axnol'mal tosaid zero graduation line of saidscale member for SBlVll'lg as a guide when setting a point of said measuring instrument.

.2. A device as set forth'in claim ,1, and in which said guiding means is in the form. of a finger having a portion thereof extending over a portion ofsaid annular series of graduation lines.

A device as set forth in claim 1, and in which said support comprises a frame part having a bearing for rotatably supporting said member having said annular series of graduation lines.

'4. A device set forth in claim 1, and in which said support comprises an annular frame part serving as a bearing for the peripheral portion of said rotatably mounted member.

5. A. device as set forth in claim 1, and in which said support comprises an elongated portion for supporting said elon ated scale member.

.6. Adevice as set forth in claim 1, and in which said support comprises an elongated portion for supporting said elongated scale member, and means for clamping said elongated scale member .to asaidielongated portion of said support.

5 6 7. A device as set forth in claim 1, andinwhich port, and means for clamping said rotatably said support comprises a frame part having a mounted member to said annular frame part. bearing for rotatably supporting said member ALOYSIUS S. MCDONNELL.

having said annular series of graduation lines, and means for clamping said rotatably mounted 5 REFERENCEs CITED member to Sam annular frame part- The following references are of record in the 8. A device as set forth in claim 1, and in which file of this patent:

said support comprises a frame part having a bearin for rotatably supporting said member UNITED STATES PATENTS having said annular series of graduation lines, and 10 Number Name Date in which said support comprises an elongated p 313,552 Sweet Mar. 10, 1885 tion for supporting said elongated scale member- 452,054 Sperry May 12, 1891 9. A device as set forth in claim 1, and in which 962,702 Diracca June 23, 1910 said support comprises a frame pa t having a 1,290,343 Posner Jan. '7, 1919 hearing for rotatably supporting said mem r 15 2,039,231 Lindner Apr. 28, 1936 having said annular series of graduation lines, and 2 370 741 McDonnen M r, 1945 in which said support comprises an elongated portion for supporting said elongated scale mem- FOREIGN PATENTS ber, means for clamping said elongated scale Number Country Date member to said elongated portion of said sup- 20 695,384 France Sept. 29, 1930 

